1. Field of the Invention
This invention relates to aqueous latex compositions that are useful in the thermoplastic fabrication of solid surface materials, solid surface materials from such compositions, and solid surface materials having unique decorative patterns.
2. Description of the Related Art
Solid surface materials are essentially non-porous composites of finely divided mineral fillers dispersed in an organic polymer matrix. Examples of commonly used fillers include calcium carbonate, silica, and alumina. Examples of commonly used polymeric materials include acrylic, polyester, and epoxy resins. Most solid surface materials are manufactured by thermoset processing, such as sheet casting, cell casting or bulk molding. The decorative qualities of such products are greatly enhanced by incorporating pigments and colored particles in patterns such that the composite resembles natural stone. The range of patterns commercially available is constrained by the intermediates and methods currently used in the fabrication of such materials.
Solid surface materials in their various applications serve both functional and decorative purposes. Since their utility is enhanced by incorporating various attractive and/or unique decorative patterns, such patterns constitute intrinsically useful properties which differentiate one product from another. The same principle applies to naturally occurring materials such as wood or stone whose utility, for example in furniture construction, is enhanced by certain naturally occurring patterns, e.g., grain, color variations, veins, strata, inclusions, and others. Commercially manufactured solid surface materials often incorporate decorative patterns intended to imitate or resemble the naturally occurring patterns in granite or marble. However, due to limitations of feasibility and/or practicality, certain decorative patterns and/or categories of decorative patterns have not previously been incorporated in solid surface materials.
In addition, it has not been possible to form compression molded articles with acceptable physical properties using conventional mineral filled thermoset polymeric particles. These conventional particles are generally made from filled thermoset polymeric material which is ground into small particles. The polymeric material is crosslinked and consequently, during compression molding the polymer chains cannot diffuse between domains to create a strong interface. In addition, the grinding process results in uncovered filler exposed on the surface of the ground particles. In general, compression molding of such ground polymeric particles results in only a weak interface between particles and the resulting article is mechanically weaker than the articles made by conventional thermoset techniques.
Decorative patterns have been previously achieved in traditional thermoset fabrication primarily by the following three methods:
(i) Monochromatic pieces of a pre-existing solid surface product is mechanically ground to produce irregularly shaped colored particles which are then combined with other ingredients in a new thermoset formulation. Casting or molding, and curing the reaction combination produces a solid surface material in which colored inclusions of irregular shapes and sizes are surrounded by, and embedded in a continuous matrix of a different color. PA1 (ii) During casting of a thermoset reaction combination, a second reaction combination of a different color is added in such a way that the two only intermix to a limited degree. In the resulting solid surface material, the different colored domains have smooth shapes and are separated by regions with continuous color variation. PA1 (iii) Different colored solid surface products are cut or machined into various shapes which are then joined by means of adhesive to create multi-colored inlayed patterns or designs. PA1 (a) about 20-60% by weight, based on the weight of solids, of at least one thermoplastic polymer having a T.sub.g greater than about 60.degree. C., the at least one thermoplastic polymer in the form of colloidal particles; PA1 (b) about 20-80% by weight, based on the weight of solids, of mineral filler particles; PA1 (c) up to about 5% by weight, based on the weight of solids, of decorative particles; PA1 (d) up to about 50% by weight, based on the weight of solids, of polymeric particles selected from filled polymeric particles, unfilled polymeric particles, and combinations thereof.
Using these traditional thermoset methods it is not possible to produce certain categories of decorative patterns which occur in natural stone. Moreover, the inclusions incorporated in solid surface products produced by method (i) are limited to sizes less than about 20 mm, more generally less than 5 mm, and must constitute less than about 80% of the thermoset reaction mix, more generally less than 20%.